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HD 122444


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F, G and K stars in the ROSAT all-sky survey. I. Photometry
We present accurate BV(RI)_c photometry for a sample of F, G and K starsdetected in selected areas of the ROSAT all-sky survey (RASS). We haveused the photometry, in addition to low-resolution spectroscopy, toestimate spectral classifications, distances and X-ray luminosities. Thelog (L_X / L_V) in the sample lies below -2. Although the samplecontains also nearby, inactive stars, it is dominated by active objects.The median X-ray luminosity in our sample is < L_X > = 29.88 andthe mean value of the hardness ratios = 0.13 +/- 0.35. Wecompare the derived X-ray luminosity function with similar functionsobtained from the serendipitous samples of the Einstein Observatorymedium sensitivity survey (EMSS) and EXOSAT. Our sample is completelyconsistent with the EMSS sample of solar type stars, indicating thatboth our sources and the EMSS sources are representative of the highgalactic latitude X-ray stellar population. We do not find extremelyactive stars (log (L_X) >= 32), as are found in the EMSS sample, andwe argue that these objects are rare. Table 3 is also available inelectronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr(130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html

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Dades d'Observació i Astrometria

Constel·lació:Virgo
Ascensió Recta:14h01m52.13s
Declinació:+00°25'20.3"
Magnitud Aparent:8.338
Distancia:64.103 parsecs
Moviment propi RA:-89.7
Moviment propi Dec:-46.5
B-T magnitude:8.977
V-T magnitude:8.391

Catàlegs i designacions:
Noms Propis
HD 1989HD 122444
TYCHO-2 2000TYC 316-893-1
USNO-A2.0USNO-A2 0900-07557051
HIPHIP 68539

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